Meat that is barbecued, grilled or fried may contribute to accelerated ageing and Alzheimer's, a study suggests.
Fatty and sugary foods could also be playing a part by boosting levels of harmful compounds called advanced glycation endproducts (Ages).
Scientists in the US found evidence that diet-related Ages might aid the development of dementia by suppressing a protective anti-ageing enzyme.
Previous research has linked abnormally low levels of the enzyme, Sirt1, to age-related brain and metabolic diseases.
Ages are formed by sugar reacting with amino acids, the building blocks of proteins.
They are abundant in "browned" meat cooked at high temperatures.
Researchers writing in the journal 'Proceedings of the National Academy of Sciences' fed mice Ages at typical Western diet levels. Unlike animals not given a high-Age diet, they were found to have low levels of Sirt1 in their blood and brain tissue.
Crucially, they also accumulated deposits of amyloid-beta protein in their brains, a key biomarker of Alzheimer's.
The scientists, led by Professor Helen Vlassara, from Mount Sinai School of Medicine in New York, wrote: "Because Ages can be modified in humans, recognition that this under-appreciated risk factor plays a role in AD (age-related dementia) and MS (metabolic syndrome) may open unique therapeutic avenues."